Field of the Invention
Exemplary embodiments of the present invention relate to a fuel processor used to shift natural gas to reformed gas easily supplied to a fuel cell stack, and more particularly, to a fuel processor including a burner unit disposed to vertically down high temperature flame generated from a burner to improve reaction time and temperature of a steam reforming unit and thermal efficiency of a heat exchanger unit.
Description of the Related Art
Generally, a fuel processor is configured to include a steam reformer shifting natural gas to hydrogen using steam reforming, high temperature shift and low temperature shift (HTS, LTS) reformers  reformer , shifting carbon monoxide generated together with hydrogen into carbon dioxide, and a burner supplying a heat quantity.
That is, main components of the natural gas are methane (CH4) and react to steam in the steam reformer to generate hydrogen and carbon monoxide. In this case, the reaction temperature generally ranges from about 650 to 700□C. and the reaction is endothermic reaction and therefore the heat quantity required for the reaction is supplied by the burner.
When the carbon monoxide generated together with the hydrogen is introduced into a fuel cell stack, the fuel cell stack is poisoned and performance of the fuel cell stack is thus adversely affected. To remove the carbon monoxide, the carbon monoxide is shifted to the carbon dioxide by the high temperature shift (HTS) reformer and the low temperature shift (LTS) reformer.
The shift reaction temperature of the HTS and the LTS generally ranges from about 300 to 350□C. in the case of the high temperature shift reformer and about 180 to 250□C. in the case of the low temperature shift reformer, and the shift reaction diffuses heat at the time of the reaction by exothermic reaction.
The burner is positioned in a combustion chamber of the fuel processor to perform combustion and combustion exhaust gas generated during the combustion process ascends toward a top layer of the fuel processor and then passes through a channel between a catalytic reformer and the combustion chamber from top to bottom to supply heat to the catalytic reformer.
As described above, the existing fuel processor separately uses the reformer by being divided into the steam reformer and the shift reformer. In this case, the steam reformer uses the endothermic reaction and the shift reformer uses the exothermic reaction and therefore the steam reformer and the shift reformer have different thermal gradients and a large difference in reaction temperature. Therefore, the steam reformer and the shift reformer are separately manufactured, such that the internal structure and the channel may be complicated and the entire volume of the reformer may be increased.